1. Field of the Invention
The present invention relates to a chucking device for a magnetic disk.
2. Description of the Related Art
A magnetic disk typified by a flexible disk is loaded, in the form of a disk cartridge in which a thin film recording disk is received in a case into a magnetic disk drive device. The recording disk is rotated in this magnetic disk drive device, and input/output of recording is carried out through a writing/reading window with a shutter, which is bored in the case. This recording disk must be easily attached/detached while it is received in the case. Further, it must be accurately aligned with a rotating shaft of the magnetic disk drive device at writing/reading, and the rotating speed must be accurately controlled. Thus, conventionally, a chucking device shown in FIG. 7 and FIG. 8 is used in the magnetic disk drive device.
A center hub made of a ferromagnetic metal disk or the like is fitted to the center part of the recording disk of the flexible disk. In FIGS. 7 and 8, this center hub 2 is provided with a substantially square center hole 3 at its center part, and a substantially rectangular drive hole 4 at its peripheral part. This drive hole 4 includes a front edge 4a at the front in a rotor yoke rotation direction and an outside edge 4b in a direction (hereinafter referred to as xe2x80x9coutwardxe2x80x9d in the present specification) away from the rotation center of the rotor yoke.
On the other hand, the magnetic disk drive device is provided with a rotor yoke 101 made of a ferromagnetic metal disk and rotationally driven by a motor (not shown) in a constant direction (denoted by xe2x80x9cDxe2x80x9d in the drawing), and a magnetic disk (chucking magnet) 102 is fixed thereon.
A center shaft 103 is provided in a standing manner at the rotation center O of the rotor yoke 101. This center shaft 103 extends through an opening 102a of the center part of the magnetic disk 102 and is loosely inserted into the center hole 3 of the center hub.
In the present specification, xe2x80x9clooselyxe2x80x9d means a state in which a free movement can be made within a predetermined range in the horizontal direction and the vertical direction.
A drive pin through hole 104 is formed into an arc shape along a circumference at a peripheral part of the rotor yoke 101. A chucking arm 105 molded into an arc shape along the circumference is fitted in the drive pin through hole 104. The chucking arm 105 is provided with a drive pin 106 extending upward at a tip part (hereinafter referred to as xe2x80x9cfront partxe2x80x9d) 105a directed toward a rotation direction D of the rotor yoke 101. This drive pin 106 loosely passes through a front opening 102b formed in the magnetic disk 102 and is loosely inserted into the drive hole 4 of the center hub.
On the other hand, a fixing hole 105c is provided at the other end (hereinafter referred to as xe2x80x9crear partxe2x80x9d) 105b of the chucking arm 105. Further, a hole part 101a corresponding to the fixing hole 105c is also provided in the rotor yoke 101 and the magnetic disk 102. A fixing pin 101b passing through the fixing hole 105c and the hole part 101a locks the chucking arm 105 to the rotor yoke 101. The chucking arm 105 can swing with this fixing pin 101b as the center in the horizontal direction within the range of the width of the drive pin through hole 104.
When the flexible disk is loaded in this magnetic disk drive device, the recording disk is placed on the rotor yoke 101. The center hub 2 fitted to the recording disk is magnetically attracted by the magnetic disk 102, and the center hole 3 of the center hub receives the center shaft 103 at the side of the rotor yoke. At this point, the drive pin 106 projecting upward from the magnetic disk 102 may or may not be inserted in the drive hole 4 of the center hub. In case the magnetic disk 102 is not inserted, the center hub 2 presses the drive pin 106, which is pushed to the level of the lower surface of the center hub 2.
Here, when a motor (not shown) makes at most one turn to the rotor yoke 101 in the D direction, the top of the drive pin 106 slides and rotates on the lower surface of the center hub, and is received into the drive hole 4 and raised. When the rotor yoke 101 is further rotated in the D direction in this state, the chucking arm 105 is swung in the direction in which the drive pin 106 comes away from the rotation center O by the centrifugal force due to rotation of the rotor yoke 101. The drive pin 106 then comes in contact with the outside edge 4b of the drive hole 4 and swings and moves forward in the drive hole 4 through the rotating force of the rotor yoke 101. The drive pin 106 comes in contact with the front edge 4a of the drive hole 4 as well. As a result, the drive pin 106 comes in contact with two sides of the front edge 4a and the outside edge 4b of the drive hole 4 and is supported. This state is hereinafter referred to as xe2x80x9cfront/outside supportxe2x80x9d.
At this time, the center shaft 103 comes in contact with two adjacent sides 3a and 3b of the center hole 3 of the center hub at the side facing the drive pin 106 across the rotation center O. In this state, the center of the recording disk coincides with the rotating shaft O of the rotor yoke 101 and chucking is completed. In this state, the recording disk of the flexible disk is not decentered and can accurately follow the controlled rotation speed of the rotor yoke 101 to rotate.
However, in the conventional chucking apparatus, the fixing pin 101b is used for the swing of the chucking arm 105 to realize the front/outside support of the drive pin 106, which increases the number of parts. Further, in order to manufacture this chucking apparatus, positioning and boring of the fixing hole 105c and the hole part 101a, caulking fixation of the fixing pin 101b and the like become necessary. These make manufacture and assembly troublesome and the manufacturing cost high.
The present invention provides a chucking device for a magnetic disk, which realizes a front/outside support by inexpensive means, prevents decentering rotation of a recording disk, and always enables accurate writing/reading.
To achieve the above object, the present invention adopts the following structure.
A chucking device for a magnetic disk of the invention comprises a substantially disk-shaped bearing provided on a surface of a base body and having an outer peripheral side surface, a rotor yoke disposed on the bearing and rotating in a constant direction while having a center hub of a magnetic disk placed thereon, a center shaft provided from the bearing to pass through a rotation center of the rotor yoke and loosely inserted into a center hole of the center hub, and a drive arm extending in a circumferential direction in a rear side of the rotor yoke and loosely suspended from and held by the rotor yoke at both ends thereof. The chucking device is characterized in that an inner peripheral surface for restraining the drive arm moving toward the bearing is formed along an outer peripheral side surface of the bearing at an inner peripheral side of the drive arm. A drive pin is formed at a front part of the drive arm in a rotor yoke rotation direction, which loosely passes through a drive pin through hole formed in the rotor yoke and extends toward a surface side of the rotor yoke, and is loosely inserted into a drive hole formed at a peripheral part of the center hub and having a front edge at a front part in the rotor yoke rotation direction and an outside edge in a direction away from a rotation center of the rotor yoke. A rear edge part of the drive pin through hole is enabled to come in contact with the drive pin. A locking flange for loosely locking the drive pin is provided at an outer edge part thereof. When the rotor yoke having the magnetic disk placed thereon is rotated, the inner peripheral surface of the drive arm comes away from the outer peripheral side surface, the drive pin is engaged with the locking flange, and the drive pin comes in contact with the front edge and the outside edge of the drive hole.
The chucking device for a magnetic disk of the invention is also characterized in that the drive arm is suspended from and held by the rotor yoke through a front flange capable of loosely engaging the locking flange of the drive pin through hole, a rear flange is formed at a rear part of the drive arm and placed on an upper surface of the rotor yoke behind the drive arm, and the inner peripheral surface is restrained by the outer peripheral side surface of the bearing.
Further, the chucking device of the invention is characterized in that the engagement of the front flange with the locking flange is kept in a state in which the inner peripheral surface of the drive arm is in contact with the outer peripheral side surface. A cutout part is formed at a front side of the drive pin in the rotation direction, which is engaged with the locking flange. Movement of the drive arm toward the front side in the rotation direction is restrained.
Since the inner peripheral surface for restraining the drive arm from moving toward the bearing side is formed at the inner peripheral side of the drive arm, the drive arm is not largely shifted to the bearing side. Thus, there is no risk that the drive arm will fall off from the rotor yoke although the drive arm is not fixed by a fixing pin.
Also, when the rotor yoke having the magnetic disk placed thereon is rotated, the drive arm and the bearing do not swing mutually and the rotation of the rotor yoke is not hindered since the inner peripheral surface of the drive arm comes away from the bearing. At the same time, the abrasion of the drive arm itself can be prevented.
Even if the rotor yoke is rotated and the inner peripheral surface of the drive arm comes away from the outer peripheral side surface, there is no risk that the drive arm will fall off from the rotor yoke since the drive pin is engaged with the locking flange.
Moreover, since the drive arm is suspended from and held by the rotor yoke through the front flange, the rear flange, and the inner peripheral surface, the drive arm is easily swung to the outer peripheral side by the centrifugal force generated by the rotation of the rotor yoke, and the front/outside support can be realized.
Further, even when the inner peripheral surface of the drive arm is in contact with the outer peripheral side surface, there is no risk that the drive arm will fall off from the rotor yoke since the front flange is engaged with the locking flange.
Furthermore, the cutout is formed at the front of the drive arm in the rotation direction, and this cutout is engaged with the locking flange so the movement of the drive arm toward the front side in the rotation direction is restrained. Thus, the drive arm can be certainly suspended from and held by the rotor yoke, and the drive arm does not fall off from the rotor yoke.